Introducer sheaths are important instruments for use in medical diagnostic and therapeutic procedures. In particular, introducer sheaths can be used by a clinician to access target areas of the patient's anatomy, e.g., the patient's cardiovascular system, and also allow for diagnostic and/or therapeutic payloads (such as ablation catheters) to be inserted into these target areas. Introducer sheaths often include hemostasis valves that permit introduction of the desired payloads but at the same time inhibit undesired fluid loss from the introducer sheath.